In-situ monitor seed for copper plating

ABSTRACT

A method and apparatus for monitoring copper seed layer growth during copper plating of a semiconductor wafer. A ring contact for use in copper plating of the semiconductor wafer is generally divided into a plurality of switches thereof. The ring contact is biased to prior to copper plating of the semiconductor wafer to determine a copper seed layer conductivity. Each switch among the plurality of switches can be connected together and thereafter the switches may be biased to an anode during copper plating, thereby permitting in-situ monitoring of copper seed resistance prior to the copper plating and a detection of copper seed damage and copper seed corrosion associated with the copper plating.

TECHNICAL FIELD

[0001] The present invention relates generally to semiconductor fabrication techniques and devices. The present invention also relates to copper plating devices and techniques utilized in the fabrication of integrated circuits on semiconductor wafers. The present invention also relates to contact rings utilized in copper plating processes and devices.

BACKGROUND OF THE INVENTION

[0002] The production of semiconductor integrated circuits and other microelectronic devices from workpieces such as semiconductor wafers typically requires formation of one or more metal layers on the wafer. These metal layers are used, for example, to electrically interconnect the various devices of the integrated circuit. Further, the structures formed from the metal layers may constitute microelectronic devices such as read/write heads, etc.

[0003] The microelectronic manufacturing industry has applied a wide range of metals to form such structures. These metals include, for example, nickel, tungsten, solder, platinum, and copper. Further, a wide range of processing techniques have been used to deposit such metals. These techniques include, for example, chemical vapor deposition (CVD), physical vapor deposition (PVD), electroplating, and electroless plating. Of these techniques, electroplating and electroless plating tend to be the most economical and, as such, the most desirable. Electroplating and electroless plating can be used in the deposition of blanket metal layers as well as patterned metal layers.

[0004] One of the most popular process sequences used by the microelectronic manufacturing industry to deposit a metal onto semiconductor wafers is referred to as “damascene” processing. In such processing holes, commonly called “vias”, trenches and/or other recesses are formed onto a workpiece and filled with a metal, such as copper. In the damascene process, the wafer is first provided with a metallic seed layer which is used to conduct electrical current during a subsequent metal electroplating step.

[0005] If a metal such as copper is utilized, the seed layer can be disposed over a barrier layer material, such as Ti, TiN, etc. The seed layer is generally a very thin layer of metal which can be applied using one or more of several processes. For example, the seed layer of metal can be laid down using physical vapor deposition or chemical vapor deposition processes to produce a layer on the order of 1,000 angstroms thick. The seed layer can advantageously be formed of copper, gold, nickel, palladium, or other metals. The seed layer is formed over a surface which is convoluted by the presence of the vias, trenches, or other recessed device features.

[0006] A metal layer is then electroplated onto the seed layer in the form of a blanket layer. The blanket layer is plated to form an overlying layer, with the goal of providing a metal layer that fills the trenches and vias and extends a certain amount above these features. Such a blanket layer will typically have a thickness on the order of 10,000 to 15,000 angstroms (1-1.5 microns).

[0007] After the blanket layer has been electroplated onto the semiconductor wafer, excess metal material present outside of the vias, trenches, or other recesses is removed. The metal is removed to provide a resulting pattern of metal layer in the semiconductor integrated circuit being formed. The excess plated material can be removed, for example, using chemical mechanical planarization. Chemical mechanical planarization is a processing step which uses the combined action of a chemical removal agent and an abrasive which grinds and polishes the exposed metal surface to remove undesired parts of the metal layer applied in the electroplating step.

[0008] The electroplating of the semiconductor wafers takes place in a reactor assembly. In such an assembly an anode electrode is disposed in a plating bath, and the wafer with the seed layer thereon is used as a cathode. Only a lower face of the wafer contacts the surface of the plating bath. The wafer is held by a support system that also conducts the requisite electroplating power (e.g., cathode current) to the wafer. The support system may comprise conductive fingers that secure the wafer in place and also contact the wafer seed layer in order to conduct electrical current for the plating operation.

[0009] Thus, the modern semiconductor industry has begun relying on a manufacturing process called “damascene” for forming interconnect lines and vias for multi-layer metal structures that provide the “wiring” of an integrated circuit. As explained above, the damascene technique involves etching a trench in a planar dielectric (insulator) layer and filling the trench with a metal such as aluminum, copper, or tungsten. A technique called “dual-damascene” adds etched vias for providing contact to the lower level as the damascene structure is filled.

[0010] There are several different ways to manufacture the damascene structure in the dielectric layer as practiced in the art For example, when copper is used as the filling, a layer of another material can be initially deposited to line the trenches and vias to prevent the migration of the copper into the dielectric layer. This migration barrier can be deposited by chemical vapor deposition (CVD), physical vapor deposition (PVD), or electroless deposition. In addition to the migration barrier, sometimes a seed layer of the plating metal and/or other metals are applied to serve as a good site for electroless or electrolytic plating.

[0011] The filling process can be accomplished by plasma deposition, sputtering, or electroless or electrolytic deposition onto a seed layer. To achieve good fill of the typical micron to sub-micron wide trenches and vias, extra metal is deposited in the process, such metal covering areas of the wafer above and outside the trenches and vias. After filling, the extra metal must be removed down to the dielectric surface while leaving the trenches and vias filled in a process called “planarization”. Standard chemical mechanical planarization (CMP) can be used to provide a planarized surface and metal removal.

[0012] As an alternative to CMP, electrochemical etching (ECE), electrochemical polishing (ECP), electropolishing or electrochemical planarization (ECP) has been used. For the purpose of this application, the terms “electrochemical polishing”, “electropolishing”, “planarizing” and “electrochemical planarization” will be used interchangeably as they are in literature, the end goal is to have a very flat and smooth surface, the small differences between the terms is that the polishing desires to have a very smooth surface, while planarization desires to flatten-out topology and produce a flat smooth surface. “Electrochemical etch” however has a different purpose, that is to remove material, generally uniformly, without regard to surface flatness.

[0013] In conventional copper plating devices, a barrier/seed is required for current conduction and copper growth. For the production of semiconductor wafers, however, patterns are located on the top of the wafer and cannot be monitored in-situ effectively. In addition, some wafers may be mis-processed and seed layer processes skipped prior to ECP. Wafers that do not have a copper seed layer or a poorly plated seed layer, which then are sent to ECP operations can cause a great amount of copper to accumulate on the associated ring contact utilized in copper plating and semiconductor fabrication operations thereof. This results in particle accumulation issues and wafer peeling concerns. Conventional approaches to minimize this problem typically involves setting a high voltage value. Such an approach, however, will only reduce the particle risk while completely eliminating the risk altogether. Based on the foregoing, the present inventors have concluded that a need exists for an improved apparatus and method for in-situ monitoring of metal seed layer formation.

BRIEF SUMMARY OF THE INVENTION

[0014] The following summary of the invention is provided to facilitate an understanding of some of the innovative features unique to the present invention, and is not intended to be a full description. A full appreciation of the various aspects of the invention can be gained by taking the entire specification, claims, drawings, and abstract as a whole.

[0015] It is therefore one aspect of the present invention to provide an improved semiconductor fabrication apparatus and method.

[0016] It is another aspect of the present invention to provide improved copper plating devices and techniques utilized in the fabrication of integrated circuits on semiconductor wafers.

[0017] It is yet another aspect of the present invention to provide an improved contact ring for utilization in copper plating processes and devices thereof.

[0018] It is still another aspect of the present invention to provide a method and apparatus for monitoring copper seed layer growth during copper plating of a semiconductor wafer.

[0019] The above and other aspects of the present invention can thus be achieved as is now described. A method and apparatus for monitoring copper seed layer growth during copper plating of a semiconductor wafer is disclosed herein. A ring contact for use in copper plating of the semiconductor wafer is generally divided into a plurality of switches thereof. The ring contact is biased to prior to copper plating of the semiconductor wafer to determine a copper seed layer conductivity. Each switch among the plurality of switches can be connected together and thereafter the switches may be biased to an anode during copper plating, thereby permitting in-situ monitoring of copper seed resistance prior to the copper plating and a detection of copper seed damage and copper seed corrosion associated with the copper plating. The ring contact can preferably be divided into 2 to 32 switches. The ring contact can be biased to check the seed layer conductivity before plating. All ring contacts can be connected together and biased to an anode during plating. In-situ monitoring of the seed resistance before plating thus can take place according to the method and apparatus disclosed herein. Seed damage or seed corrosion can thus be detected, thereby preventing particle and copper peeling on damaged seed or non-seed layers thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying figures, in which like reference numerals refer to identical or functionally-similar elements throughout the separate views and which are incorporated in and form part of the specification, further illustrate the present invention and, together with the detailed description of the invention, serve to explain the principles of the present invention.

[0021]FIG. 1 illustrates a side view of a copper plating apparatus, in accordance with a preferred embodiment of the present invention.

[0022]FIG. 2 depicts a top side view of a copper plating apparatus, in accordance with a preferred embodiment of the present invention;

[0023]FIG. 3 illustrates a schematic diagram of a copper plating apparatus, in accordance with a preferred embodiment of the present invention;

[0024]FIG. 4 depicts a top view of the copper plating apparatus indicated in FIG. 1, in accordance with a preferred embodiment of the present invention;

[0025]FIG. 5 illustrates a top view of the copper plating apparatus indicated in FIG. 2, in accordance with a preferred embodiment of the present invention;

[0026]FIG. 6 depicts a schematic diagram of a contact ring that can be utilized in accordance with a preferred embodiment of the present invention; and

[0027]FIG. 7 illustrates a block diagram of a semiconductor wafer and a copper plating apparatus, in accordance with a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0028] The particular values and configurations discussed in these non-limiting examples can be varied and are cited merely to illustrate embodiments of the present invention and are not intended to limit the scope of the invention.

[0029] Because a barrier/seed is required for current conduction and copper growth in traditional copper plating devices and related methods thereof, particle accumulation, along with copper peeling and copper seed corrosion must be resolved. In the production of semiconductor wafers, patterns are generally located on the top of the wafer and cannot be monitored in-situ effectively.

[0030] Some semiconductor wafers may be mis-processed and seed layer processes skipped prior to ECP. Wafers that do not have a copper seed layer or a poorly plated seed layer, which then are sent to ECP operations can cause a great amount of copper to accumulate on the associated ring contact utilized in copper plating and semiconductor fabrication operations thereof. This results in particle accumulation issues and wafer peeling concerns.

[0031] Conventional approaches to minimize this problem typically involves setting a high voltage value. Such an approach, however, reduces the particle risk while not entirely completing elimination. The present invention disclosed and described herein thus solves these problems and associated issues.

[0032]FIG. 1 illustrates a side view 10 of a copper plating apparatus 21, in accordance with a preferred embodiment of the present invention. Copper plating apparatus 21 generally includes a copper anode 16 having a positive node 17. The electrolyte flow is indicated by arrow 18. Note that in FIGS. 1 to 5 illustrated herein, like parts are generally indicated by identical reference numerals.

[0033]FIG. 2 depicts a top side view 12 of a copper plating apparatus 23, in accordance with a preferred embodiment of the present invention. Copper plating apparatus 23 of FIG. 2 is analogous to copper plating apparatus of 21 of FIG. 1. Copper plating apparatus 23 includes a ring 22 (i.e., a contact ring). FIG. 3 illustrates a schematic diagram 15 of a copper plating apparatus, in accordance with a preferred embodiment of the present invention. Note the inclusion of ground 19 and positive node 17.

[0034] Because contact rings are well-known in the semiconductor arts, it is not necessary to describe such contact rings in detail. It is important, however, to keep in mind that the present invention generally comprises an improvement to prior art contact rings and the manner in which such contact rings are utilized, in order to effect a novel method and apparatus for in-situ monitoring of seed layer development and ensuring proper contact and no wafer warpage. In general, a contact ring can be utilized to provide a substantially continuous electrically-conductive contact with a peripheral region of an associated semiconductor wafer or other workpiece. The improved contact ring disclosed herein, however, permits the periphery of a semiconductor wafer to be checked and/or monitored for copper seed layer formation only, not the center of the semiconductor wafer.

[0035]FIG. 4 depicts a top view 23 of the copper plating apparatus 21 indicated in FIG. 1, in accordance with a preferred embodiment of the present invention. Copper plating apparatus 21 can be configured as a ring contact which is divided into a plurality of 2 to 32 switches 24. The number of switches chosen depends on a desired implementation of the present invention. Thus, the number of switches may vary. An initial switch T_(i) is represented in FIG. 4 by arrow 26. A second switch is indicated by arrow 28.

[0036]FIG. 5 illustrates a top view 25 of the copper plating apparatus 22 indicated in FIG. 2, in accordance with a preferred embodiment of the present invention. Block 32 illustrated in FIG. 5 represents a computer controller. Also illustrated in FIG. 5 are a positive node 17 and a negative node 19. A central portion 30 of copper plating apparatus 22 may be linked to computer controller 32. Again, in FIGS. 4 and 5, like parts are illustrated by identical reference numerals.

[0037]FIG. 6 depicts a schematic diagram 44 of a contact ring 42 that can be utilized in accordance with a preferred embodiment of the present invention. Contact ring 42 generally comprises a contact ring which can be divided into separate contacts, such as, for example, contact 46 to detect seed quality and contact. In addition, contact ring 48 is divided in such a manner to detect the seed resistance by making switches on the contact ring. Thus, contact ring 42 can be divided into a plurality of switches or contacts in order to effectively introduce in-situ monitoring of seed uniforming prior to plating, such as, for example, copper plating. Contact ring 42 can also be configured from a rigid and non-corrosive materials, such as for example, Ti.

[0038] Such a configuration is also desired to assure that semiconductor wafers are properly moved into a plating cell and that no copper slum is deposited on the contact ring 42. FIG. 7 illustrates a block diagram 53 of a semiconductor wafer 50 and a copper plating apparatus, in accordance with a preferred embodiment of the present invention. In addition, a quartz portion 58 is illustrated in FIG. 7. Semiconductor wafer 50 may be utilized in association with contact ring 42 depicted in FIG. 6. By configuring a copper plating apparatus in the manner illustrated in FIGS. 6 and 7, proper contact may be assured with a minimized downward force, which is indicated by arrow 56 in FIG. 7, thereby reducing low k peeling. All contacts are thus joined with an inside metal ring.

[0039] Based on the foregoing, it can be appreciated that the present invention generally discloses a method and apparatus for monitoring copper seed layer growth during copper plating of a semiconductor wafer is disclosed herein. A ring contact for use in copper plating of the semiconductor wafer is generally divided into a plurality of switches thereof. The ring contact is biased to prior to copper plating of the semiconductor wafer to determine a copper seed layer conductivity.

[0040] Each switch among the plurality of switches can be connected together and thereafter the switches may be biased to an anode during copper plating, thereby permitting in-situ monitoring of copper seed resistance prior to the copper plating and a detection of copper seed damage and copper seed corrosion associated with the copper plating.

[0041] The ring contact can preferably be divided into 2 to 32 switches. The ring contact can be biased to check the seed layer conductivity before plating. All ring contacts can be connected together and biased to an anode during plating. In-situ monitoring of the seed resistance before plating thus can take place according to the method and apparatus disclosed herein. Seed damage or seed corrosion can thus be detected, thereby preventing particle and copper peeling on damaged seed or non-seed layers thereof.

[0042] The embodiments and examples set forth herein are presented to best explain the present invention and its practical application and to thereby enable those skilled in the art to make and utilize the invention. Those skilled in the art, however, will recognize that the foregoing description and examples have been presented for the purpose of illustration and example only. Other variations and modifications of the present invention will be apparent to those of skill in the art, and it is the intent of the appended claims that such variations and modifications be covered. For example, although the present invention is discussed in terms of “copper plating,” it is anticipated that the present invention applies equally to other types of metallic plating, not merely copper.

[0043] The description as set forth is thus not intended to be exhaustive or to limit the scope of the invention. Many modifications and variations are possible in light of the above teaching without departing from scope of the following claims. It is contemplated that the use of the present invention can involve components having different characteristics. It is intended that the scope of the present invention be defined by the claims appended hereto, giving full cognizance to equivalents in all respects. 

1. A method for monitoring seed layer growth during plating of a semiconductor wafer, said method comprising the steps of: dividing a ring contact for use in plating of said semiconductor wafer, wherein said ring contact is divided to include a plurality of switches thereof; and biasing said ring contact prior to plating of said semiconductor wafer to determine a seed layer conductivity, thereby permitting in-situ monitoring of seed resistance prior to plating of said semiconductor wafer.
 2. The method of claim 1 further comprising the step of: connecting each switch among said plurality of switches together.
 3. The method of claim 1 further comprising the step of: biasing said plurality of switches to an anode during plating.
 4. The method of claim 1 further comprising the steps of: connecting each switch among said plurality of switches together; and biasing said plurality of switches to an anode during plating.
 5. The method of claim 1 further comprising the step of: detecting seed damage associated with said plating of said semiconductor wafer.
 6. The method of claim 1 further comprising the step of: detecting seed corrosion associated with said plating of said semiconductor wafer.
 7. The method of claim 1 further comprising the step of: plating said semiconductor wafer.
 8. The method of claim 7 wherein the step of plating said semiconductor wafer further comprises the step of: plating said semiconductor wafer with copper.
 9. The method of claim 8 wherein said seed layer comprises a copper seed layer.
 10. A method for monitoring copper seed layer growth during copper plating of a semiconductor wafer, said method comprising the steps of: dividing a ring contact for use in copper plating of said semiconductor wafer, wherein said ring contact is divided to include a plurality of switches thereof; and biasing said ring contact prior to copper plating of said semiconductor wafer to determine a copper seed layer conductivity; connecting each switch among said plurality of switches together; and thereafter biasing said plurality of switches to an anode during copper plating, thereby permitting in-situ monitoring of copper seed resistance prior to said copper plating and a detection of copper seed damage and copper seed corrosion associated with said copper plating.
 11. An apparatus for monitoring seed layer growth during plating of a semiconductor wafer, said apparatus comprising: a ring contact for use in plating of said semiconductor wafer, wherein said ring contact is divided to include a plurality of switches thereof; and biasing mechanism for biasing said ring contact prior to plating of said semiconductor wafer to determine a seed layer conductivity, thereby permitting in-situ monitoring of seed resistance prior to plating of said semiconductor wafer.
 12. The apparatus of claim 11 wherein each switch among said plurality of switches are connected together.
 13. The apparatus of claim 11 wherein said biasing mechanism further comprises: biasing mechanism for biasing said plurality of switches to an anode during plating.
 14. The apparatus of claim 11 further comprising: connecting each switch among said plurality of switches together; and wherein said biasing mechanism biases said plurality of switches to an anode during plating.
 15. The apparatus of claim 11 further comprising: detecting mechanism for detecting seed damage associated with said plating of said semiconductor wafer.
 16. The apparatus of claim 11 further comprising: detecting mechanism for detecting seed corrosion associated with said plating of said semiconductor wafer.
 17. The apparatus of claim 11 further comprising: plating mechanism for plating said semiconductor wafer.
 18. The apparatus of claim 17 wherein said plating mechanism further comprises: plating mechanism for plating copper.
 19. The apparatus of claim 18 wherein said seed layer comprises a copper seed layer.
 20. An apparatus for monitoring copper seed layer growth during copper plating of a semiconductor wafer, said apparatus comprising: a ring contact for use in copper plating of said semiconductor wafer, wherein said ring contact is divided to include a plurality of switches thereof; biasing mechanism for biasing said ring contact prior to copper plating of said semiconductor wafer to determine a copper seed layer conductivity; wherein each switch among said plurality of switches are connecting together; and wherein said plurality of switches are biased to an anode during copper plating, thereby permitting in-situ monitoring of copper seed resistance prior to said copper plating and a detection of copper seed damage and copper seed corrosion associated with said copper plating. 